Recently, along with miniaturization of a semiconductor device, resist film thickness is getting smaller in a lithography process. If the resist film thickness is reduced, it is difficult to directly process a processed film using a resist pattern as a mask. As a method for solving this problem, a multilayer resist process such as a reverse mask process has been proposed. In the reverse mask process, a reverse material is coated onto a resist pattern, and the reverse material is subjected to etch-back to expose an upper surface of the resist pattern. Then, dry etching using the reverse material as a mask is performed to remove the resist pattern, and, thus, to form a reverse pattern. By virtue of the use of the reverse pattern as a mask, the processed film can be processed into a pattern in which the resist pattern is reversed.
In the above conventional reverse mask process, a level difference corresponding to a resist pattern coverage (ratio of concave and convex portions) is formed on the coated reverse material. When the reverse material on which the coating level difference is formed is subjected to etch-back, there are problems that the reverse material remains in a region from which the reverse material is to be removed, the reverse material in a region where the reverse material is to be remained is removed, or a processed film cannot be processed into a desired pattern.
Thus, it has been studied that the coating level difference of the reverse material is reduced by arrangement of a dummy pattern and a design rule limitation. However, the arrangement of the dummy pattern is difficult in design, or there is a problem that a design flexibility is reduced due to a strict design rule limitation, and the coating level difference of the reverse material interferes with application of a reverse mask process.